Many advances in astronomy have resulted from the opening of a newobservation in a new band of the electromagnetic. The revealed the the Rays inside star nurseries and .
This is one of the reasons for the design of theAtacama Large Millimeter/submillimeter Array (Alma). Another, complementary, is that the network ofconstructed in this way makes it possible to and therefore to have a very large virtual instrument without having to create it.
Today, we learn that the Alma radio telescope network was used for a major first, to observe in the fieldmillimeter and sub-millimeter processes associated with kilonovae. Remember that these are collisions of which was first discovered in the form of short gamma rays, the nature of which has only recently been determined, although it has been suspected for decades. The energy released is colossal, which makes among the most luminous phenomena of the .
In this artist’s video, two neutron stars of low dimension but very high density are about to merge and explode into a kilonova. This particularly rare event results in the emission of gravitational waves and short gamma-ray bursts. The two emissions were actually observed on August 17, 2017, respectively by Ligo-Virgo and Fermi/Integral. Various detailed observations carried out using ESO telescopes have confirmed the nature of this object – a kilonova – located within the galaxy NGC 4993 some 130 million light-years from Earth. This type of object is the main source of heavy chemical elements, such as gold and platinum, in the Universe. © ESO
Neutron star collisions that produce gold and platinum
This time, the which talks about the observed GRB 211106A short gamma-ray burst – like its name of Gamma Ray Burst indicates, on November 6, 2021. As in the case of the source of gravitational waves (Gravitational Wave) observed on August 17, 2017, the collision between neutron stars arises from the fact that the two compacts lost energy in the form of gravitational waves faster and faster, which led them to fall inexorably and faster and faster towards each other.published an article in The Astrophysical Journal Lettersa version of which is freely available on
but also a collimated particle beam at very high also producing an equally collimated beam of high energy gamma. The Earth passed through this beam by chance like an observer illuminated by a lighthouse.
The jet of particles and gamma photons by injecting itself into the interstellar medium excites it and forces theit contains, to shine in response. It is this radiation which was detected for the first time in the spectral band accessible to Alma. Prior to this instrument, millimeters were not sensitive enough to detect these afterglows, as GRBs are often observed at billions of of the . We therefore observe only the old GRBs and we also suspect that for a still unknown reason, they were more abundant during the first billion years of the history of the cosmos. In fact, GRB 211106A occurred while the observable was only 40% of its current age. However, even if the kilonovae are clearly visible from afar in gamma, this is no longer the case with the remanent radiation which is much less luminous.
Initially, when only the X-ray counterpart of GRB 211106A was discovered using the satelliteastrophysicists thought that the kilonovae could still come from a neighboring galaxy, although we could not associate one with it. via observations in the visible with Hubble – probably due to the presence on the line of sight near the GRB of a large quantity of dust.
But finally, thanks to Alma, it was possible to find a faint and distant galaxy where the gamma-ray burst occurred. The distance determined, it was necessary to conclude that it was one of the most powerful GRBs detected to date…
Alma, in conjunction with(James Webb Space Telescope) should make it possible to go even further in the study of short gamma-ray bursts.
The GW170817 detection saga. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Science vs Cinema